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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3332) Provide an exactly-once Cassandra connector
Date Tue, 16 Feb 2016 11:17:18 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15148469#comment-15148469
] 

ASF GitHub Bot commented on FLINK-3332:
---------------------------------------

Github user rmetzger commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1640#discussion_r52997627
  
    --- Diff: flink-streaming-connectors/flink-connector-cassandra/src/main/java/org/apache/flink/streaming/connectors/cassandra/CassandraExactlyOnceSink.java
---
    @@ -0,0 +1,113 @@
    +/**
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + * <p/>
    + * http://www.apache.org/licenses/LICENSE-2.0
    + * <p/>
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +package org.apache.flink.streaming.connectors.cassandra;
    +
    +import com.datastax.driver.core.Cluster;
    +import com.datastax.driver.core.PreparedStatement;
    +import com.datastax.driver.core.ResultSet;
    +import com.datastax.driver.core.ResultSetFuture;
    +import com.datastax.driver.core.Session;
    +import com.google.common.util.concurrent.FutureCallback;
    +import com.google.common.util.concurrent.Futures;
    +import org.apache.flink.api.java.tuple.Tuple;
    +import org.apache.flink.streaming.runtime.operators.CheckpointCommitter;
    +import org.apache.flink.streaming.runtime.operators.GenericExactlyOnceSink;
    +
    +/**
    + * Sink that emits its input elements into a Cassandra database. This sink is integrated
with the checkpointing
    + * mechanism to provide near exactly-once semantics.
    + * <p/>
    + * Incoming records are stored within a {@link org.apache.flink.runtime.state.AbstractStateBackend},
and only committed if a
    + * checkpoint is completed. Should a job fail while the data is being committed, no exactly
once guarantee can be made.
    + *
    + * @param <IN> Type of the elements emitted by this sink
    + */
    +public class CassandraExactlyOnceSink<IN extends Tuple> extends GenericExactlyOnceSink<IN>
{
    +	private final String host;
    +	private final String createQuery;
    +	private final String insertQuery;
    +
    +	private transient Cluster cluster;
    +	private transient Session session;
    +	private transient PreparedStatement preparedStatement;
    +
    +	private transient Throwable exception = null;
    +
    +	public CassandraExactlyOnceSink(String host, String insertQuery, CheckpointCommitter
committer) {
    +		this(host, null, insertQuery, committer);
    +	}
    +
    +	public CassandraExactlyOnceSink(String host, String createQuery, String insertQuery,
CheckpointCommitter committer) {
    +		super(committer);
    +		if (host == null) {
    +			throw new IllegalArgumentException("Host argument must not be null.");
    +		}
    +		if (insertQuery == null) {
    +			throw new IllegalArgumentException("Insert query argument must not be null.");
    +		}
    +		this.host = host;
    +		this.createQuery = createQuery;
    +		this.insertQuery = insertQuery;
    +	}
    +
    +	@Override
    +	public void close() throws Exception {
    +		super.close();
    +		session.close();
    +		cluster.close();
    --- End diff --
    
    I would add null checks for session and cluster


> Provide an exactly-once Cassandra connector
> -------------------------------------------
>
>                 Key: FLINK-3332
>                 URL: https://issues.apache.org/jira/browse/FLINK-3332
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming Connectors
>            Reporter: Robert Metzger
>            Assignee: Chesnay Schepler
>
> With FLINK-3311, we are adding a Cassandra connector to Flink.
> It would be good to also provide an "exactly-once" C* connector.
> I would like to first discuss how we are going to implement this in Flink.



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